Simple OAuth in Rails

routes.rb

map.with_options :controller => 'user_sessions' do |session|
  session.callback '/callback', :action => 'callback'
  session.logout   '/logout',   :action => 'destroy'
  session.login    '/login',    :action => 'new'
end

sessions_controller.rb

def create
  url = TwitterOauth.get_authentication_url(session)
  redirect_to url
end

def callback
  access_token = TwitterOauth.get_access_token(session)
  screen_name  = TwitterOauth.get_screen_name(access_token)
  
  unless screen_name # Their login has failed.
    flash[:error] = "Something went horribly wrong with Twitter's OAuth."
    return redirect_to login_url
  end
  
  user = User.find_or_create_by_screen_name(screen_name)
  user.token  = access_token.token
  user.secret = access_token.secret
  if user.save
    session[:user] = user.id
    return redirect_to root_url
  end
  
  flash[:error] = "Something went horribly wrong with registration"
  return redirect_to login_url
end

twitter_oauth.rb

class TwitterOauth
  class << self
    def consumer
      OAuth::Consumer.new("token", "secret", {:site=>"http://twitter.com"})
    end

    def get_authentication_url(session)
      # Get a request token, save the session variables that we need to keep
      request_token = consumer.get_request_token
      session['oauth_request_token_token'] = request_token.token
      session['oauth_request_token_secret'] = request_token.secret
      return request_token.authorize_url
    end

    def get_access_token(session)
      # If we've already retrieved an access token
      if session['access_token_token'] and session['access_token_secret']
        access_token = OAuth::AccessToken.new(consumer, session['access_token_token'], session['access_token_secret'])
      else
        request_token = OAuth::RequestToken.new(consumer, session['oauth_request_token_token'], session['oauth_request_token_secret'])
        access_token = request_token.get_access_token
      end

      session['access_token_token']  = access_token.token
      session['access_token_secret'] = access_token.secret
  
      return access_token
    end

    def get_screen_name(access_token)
      # Whoooooo are you? Who, who - who, who
      response = consumer.request(:get, '/account/verify_credentials.json', access_token, { :scheme => :query_string })
      if response.code == "200"
        user_info = JSON.parse(response.body)        
        return user_info['screen_name'] if user_info['screen_name']
      end
      RAILS_DEFAULT_LOGGER.error "Failed to get user info via OAuth"
      return false
    end
  end
end